The dyeability of poly(lactic acid) (PLA) fiber strongly depends on disperse dye structure due to the low dyeing temperature and the short dyeing time. Thus, the dye uptake value of PLA fiber is low for some disperse dyes and is needed to be improved. In the current study, the dyeability of PLA fiber is improved with the addition of N-Phenylaminopropyl polyhedral oligomeric silsesquioxane (AP-POSS) during melt spinning process. The effects of dyeing conditions including dyeing temperature and time, disperse dye type and AP-POSS concentrations are investigated on the dyeability properties of PLA fiber samples. The tensile, thermal and morphological properties of fiber samples are also characterized by tensile testing, differential scanning calorimeter (DSC), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). As the added amount of AP-POSS increases, the percent crystallinity increases and the tensile strength reduces. According to the dyeing results, AP-POSS is very effective for increasing the dyeability of PLA fiber especially for disperse dyes with low dye uptake values.